A 60-year-old mystery was at least partly solved yesterday when pieces of a plane found lying on the seabed near Marseille were identified as coming from the wartime P-38 Lightning piloted by Antoine de Saint-Exupéry, aviator extraordinaire and author of the best-known French book of the 20th century.

Saint-Exupéry, whose classic children's book The Little Prince has been translated into more than 100 languages and still sells over a million copies a year around the world, disappeared while on a reconnaissance flight off the southern French coast on the morning of July 31 1944. No trace of the writer or his plane was found.

"No further doubt is possible, this is St-Ex's plane," said Patrick Granjean, head of the French undersea archeological research centre DRASSM. "It plunged into the sea off the island of Rioul. We don't know why and we probably never will, but it is definitely his plane."

Mr Granjean said a panel of what proved to be the P-38's turbo-compressor casing, brought to the surface last September, bore a series of four numbers - 2734 - engraved by the manufacturer, Lockheed. Records held by the National Air and SpaceMuseum near Washington showed the series correspond to the US air force registration number allocated to Saint-Exupéry's plane.

"I had tears in my eyes when it was finally confirmed," said Patrick Becker, the managing director of the undersea survey firm Geoscan which located the wreckage, reportedly spread over a strip of sea bed more than 1km long and some 400 metres wide.

The myth surrounding the mysterious disappearance of the celebrated author, the greatest cultural figure to die pour la France during the second world war and a much-needed hero in a country undermined by military defeat and humiliating occupation, has grown to extraordinary proportions over the past half-century.

Despite the possibly superior literary claims of Sartre, Mauriac and Malraux, Saint-Exupéry is the only 20th-century author to have featured on French banknotes. Lyon airport (as well as a rash of streets, schools and public buildings) were renamed after him in 2000, the centenary year of his birth, and three of his five books remain in the top 10 of the all-time French bestseller list.

St-Ex, as he is known in France, was born in Lyon in June 1900 into a deeply conservative family whose aristocratic roots dated back to the 12th century. Aged just three when his father died, he was fascinated by aviation from his first flight at the age of 12, and qualified as a pilot during national service in Strasbourg.

In 1926 he joined the Aeropostale mail service in South America, survived spectacular crashes, desert storms and rebel attacks, and pioneered the perilous mountain airline route from Buenos Aires to Patagonia - inspiration for his 1931 novel Night Flight and a 1938 collection of articles, Wind, Sand and Stars. He soon became recognised, in the words of the Belgian author Maurice Maeterlinck, as "potentially the greatest French writer of the 20th century".

At the age of 43, St-Ex was at judged too old to fly when he volunteered towards the end of the second world war. Only after lengthy persuasion was he authorised to fly five missions for the 33rd Reconnaissance Group, made up of French pilots flying US planes.

He took off from Borgo airport on Corsica at 8.45am on July 31 1944, heading across the Mediterranean in fine, clear weather to photograph German troop concentrations in the Rhône valley. Radar tracked him until he crossed the French coastline near St-Raphael at about 9.30am. He never returned to base.

The remains of many planes, including a dozen other P-38 Lightnings, were found off the coast after the war, but all proved not to have been the author's. Saint-Ex's family obstructed any systematic search, apparently on the grounds that its discovery would weaken the myth, linking the author's disappearance with that of the hero of his best-known book, The Little Prince. His friends also worried the plane's eventual discovery would renew speculation that the writer, deeply depressed at the prospect of being grounded after his final mission, crashed his plane deliberately.

Then in 1998 a Marseille fisherman, Jean-Claude Bianco, found tangled in his nets a silver identity bracelet engraved with the flyer's name, along with that of his wife Consuelo, and of the the New York publishing house, Raynal & Hitchcock, which first published The Little Prince in English in 1943.

But such was the power of the St-Ex myth that the bracelet was instantly denounced by many experts as a fake. And although amateur divers continued to turn up scattered pieces of wreckage in the same area, it was not until last year that French authorities finally gave permission for the debris to be lifted to the surface.

The two identified pieces of the Lightning, the turbo-compressor casing and part of the undercarriage, will be presented at a ceremony tomorrow in the presence of the divers and of Saint-Exupéry's descendants, a French air force spokesman said.

The core of the mystery, of course, remains. The reasons for the unexplained crash - mechanical failure, sudden illness, suicide or possibly enemy fire from the coast - will probably never be known. According to Mr Granjean, all that can be gleaned from the parts recovered so far is that the plane appears to have entered the water almost vertically, and at exceptionally high speed.